1. Field of the Invention
The present invention relates to a method of polishing a non-magnetic gadolinium gallium garnet (GGG) single crystal which is used as a base board for the epitaxial growth of a magnetic thin bubble element.
2. Prior Art
In the prior art there exists methods for polishing GGG single crystal. In such conventional methods, a polishing agent is either mixed with water to make a suspended solution or shaped into a grindstone. If such a method is applied to the base board surface of GGG single crystal, however, a surface defect commonly known as orange peel or microscopic scratches result on the polished base board surface. A commonly known method of polishing semiconductor crystals such as silicon single crystals is a mechanochemical method using a suspended mixed solution of an alkaline solution such as sodium hydroxide, potassium hydroxide, etc. and a polishing agent such as silicon dioxide and zirconium oxide. It is difficult, however, to prevent the occurrence of orange peel and microscratches by applying this method to the base board of GGG single crystals. One of the polishing methods for obtaining a crystalline base board surface for epitaxial growth with few surface defects such as orange peels and microscratches is to use colloidal silica as a polishing agent. However, since this method has very low polishing efficiency, it takes a long time to obtain a smooth and satisfactory surface.